Field of the Invention
The present invention relates to a composition for a base, and a directed self-assembly lithography method.
Discussion of the Background
Miniaturization of structures of various types of electronic devices such as semiconductor devices and liquid crystal devices has been accompanied by demands for microfabrication of patterns in lithography processes. In these days, although fine patterns having a line width of about 90 nm can be formed using, for example, an ArF excimer laser, further finer pattern formation has been required.
To meet the demands described above, a directed self-assembly lithography process which utilizes a phase separation structure constructed through directed self-assembly, as generally referred to, that spontaneously forms an ordered pattern has been proposed. As such a directed self-assembly lithography process, a method for forming an ultrafine pattern by directed self-assembly using a block copolymer that includes blocks having different properties from one another has been known (see Japanese Unexamined Patent Application, Publication No. 2008-149447, Japanese Unexamined Patent Application (Translation of PCT Application), Publication No. 2002-519728, and Japanese Unexamined Patent Application, Publication No. 2003-218383). In addition, a method of forming a fine pattern by permitting directed self-assembly of a composition that contains a plurality of polymers having properties that are different from one another has been also known (see U.S. Patent Application, Publication No. 2009/0214823, and Japanese Unexamined Patent Application, Publication No. 2010-58403). According to these methods, annealing of a film containing the polymer results in a tendency of clustering of polymer structures having the same property, and thus a pattern can be formed in a self-aligning manner.
It has been known that in such a directed self-assembly lithography process, formation of a film containing a component such as a polymer which should be subjected to the directed self-assembly on other layer may effectively cause phase separation owing to the directed self-assembly. A variety of studies have been made in connection with the layer, and formation of a variety of phase separation structures is reportedly enabled by appropriately controlling the surface free energy of the layer in permitting the directed self-assembly of the block copolymer (see Japanese Unexamined Patent Application, Publication No. 2008-36491, and Japanese Unexamined Patent Application, Publication No. 2012-174984).